This invention is directed generally to an improvement in a mounting arrangement for a temperature sensor, and more particularly to an arrangement for mounting a temperature sensor in apparatus for heating liquid.
Generally speaking, hot water heating and/or beverage brewing apparatus include a hot water reservoir from which heated water is dispensed in predetermined serving volumes through a beverage filter to a serving beaker, or directly to a hot water spigot. In many such devices, a volume of cold water is first admitted to a lower or inlet zone of the reservoir which is then heated by an electric resistance heating element within the reservoir. This heated volume is then dispensed in a volume equal to the desired serving volume from an upper outlet zone of the reservoir, coincident with the introduction of further cold water into the inlet zone.
Hence the reservoir has a volume greater than twice the serving volume so that the volume of resident heated water kept on hand is such that a further volume of heated water will be available relatively quickly following a dispensing.
In such apparatus a temperature sensing element, for example a thermistor, is disposed within the lumen of a hollow, heat-conductive tubing, extending to a predetermined depth or location in the brew-zone, at or near the center of the reservoir. This temperature sensing element produces a temperature control signal which indicates the temperature of the water in the brew-zone; i.e., the zone to which the tubing extends. Preferably, the temperature sensing element is disposed at or near the end of the tubing which extends into the reservoir.
One such beverage brewing apparatus containing a temperature sensing element disposed within a hollow tubing is shown for example in prior U.S. Pat. No. 4,531,046, which is commonly assigned herewith. In this U.S. patent, the conductive tubing is preferably constructed of a length of heat-conductive metal tubing which may be made from a copper material having a closed end which extends into the reservoir. However, other metal tubing, such as stainless steel tubing, has also been utilized for this purpose. As such, the copper or stainless steel tubing affords protection to the thermistor against exposure to the liquid within the reservoir. The rigidity of the tubing also allows the thermistor to be relatively accurately positioned near the desired central portion of the reservoir. In the above-mentioned U.S. patent, it is also suggested to accomplish the desired positioning of the thermistor by crimping or deforming the tubing segment when the thermistor had been properly positioned therein
As an additional matter, such stainless steel tubing also has a relatively long service life, even when immersed over long periods of time in hot water, and provides a reliable and relatively sanitary material for this purpose. However, the use of stainless steel material, and its fabrication into tubing of this sort has proven relatively expensive in practice.
Accordingly, we propose an alternate form of mounting arrangement for a temperature sensing element which nonetheless meets all of the requirements of mounting the same for prolonged periods of time within a hot liquid, or hot water contained in a reservoir.